Project summary Despite being one of the most central processes in biology many key questions remain about how protein translation by the ribosome is regulated. Translational control is fundamentally important for human health as dysregulation of translation is known to be involved in myriad of diseases, including numerous cancers. Our understanding of the translational control of gene expression is currently undergoing a paradigm switch. Until recently it was thought that all translational control takes place when the ribosomes decide to, or not to, initiate on a start codon. However, a wealth of recent data suggests that translation is also widely regulated after initiation has occurred, during the subsequent `elongation' phase of translation. Thus, the regulation of translation elongation is an expanding frontier for exploring the translational control of gene expression. My lab uses a powerful compliment of kinetic and genome-wide tools to investigate how the speed of ribosome elongation can be modulated to regulate gene expression. We also directly collaborate with experts to investigate both ribosome and mRNA structures. This proposal focuses on using these approaches investigate situations at the molecular level where the slow progression of the ribosome has been linked to cell health and viability, but where molecular mechanisms are unknown. Specifically, our work seeks to discover: 1) how nascent peptides modulate the rate of translation, 2) how non-canonical movements of the ribosome change gene expression, 3) how mRNA modifications impact translation rates, and 4) how post-translational modifications impact the translation machinery. These studies will provide a biochemical framework for understanding how controlling ribosome elongation rates contributes globally to gene expression. In summary, we fill crucial gaps in the burgeoning field of translation regulation via ribosome stalling mechanisms. Our studies will reveal the breadth of gene regulation via translational stalling, and dissect the molecular mechanism(s) of translational control. Overall, this work will challenge the long-held paradigm that the ribosome indiscriminately translates the majority of sequences at a mostly uniform rate. In the long-term, our findings could be key for the development of targeted therapeutics to treat diseases linked to alterations of translation elongation.